Leak detecting apparatus

ABSTRACT

A leak detecting apparatus is provided which can detect leak of a liquid injected through an injection needle into a blood vessel of a human body near its surface with high accuracy. The apparatus emits a light ray in a predetermined wavelength band containing a particular wavelength at which the reflectivity for the liquid is lower than the reflectivity for internal tissues of the human body, to the human body at a position thereof where the injection needle is inserted, and detects the light ray in the wavelength band reflected inside the human body. The apparatus measures the average intensity of the detected light ray in the wavelength band and the intensity of the detected light ray at the particular wavelength to determine an occurrence of leak when the ratio of the intensity at the particular wavelength to the measured average intensity in the wavelength band is lower than a predetermined reference value. Variations in human body or physical condition affect the whole of the wavelength band but have no effects on the relative relationships between the wavelength band and the particular wavelength. Thus, the leak of the liquid can be detected without being affected by variations in human body or physical condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/575,211, filed on Mar. 13, 2007 as the U.S. National Phase under 35U.S.C. §371 of International Application PCT/JP2005/16811, filed Sep.13, 2005, which claims priority to Japanese Patent Application No.2004-267062, filed Sep. 14, 2004, which are hereby incorporated byreference in there entirety.

TECHNICAL FIELD

The present invention relates to a leak detecting apparatus fordetecting leak of a liquid injected into a blood vessel of a human bodynear the surface thereof through an injection needle, and moreparticularly, to a leak detecting apparatus for detecting leak of aliquid injected by a chemical liquid injector.

BACKGROUND ART

Presently available medical apparatuses for capturing diagnostic imagesof patients include CT (Computed Tomography) scanners, MRI (MagneticResonance Imaging) apparatuses, PET (Positron Emission Tomography)apparatuses, ultrasonic diagnostic apparatuses and the like. Angiographyapparatuses, MRA (MR angiography) apparatuses and the like are currentlyused as medical apparatuses for capturing vascular images of patients.

When the abovementioned medical apparatuses are used, a liquid such as acontrast medium or physiological saline may be injected into a patient.Chemical liquid injectors for automatically performing the injectionhave been put into practical use. A liquid syringe, for exampleincluding a cylinder member and a piston member slidably inserted intothe cylinder member, is mounted on such a chemical liquid injector. Asyringe driving mechanism presses the piston member into the cylindermember. The cylinder member is filled with a liquid and connected to ablood vessel of a human body near the surface thereof through anextension tube and an injection needle. Thus, the liquid in the liquidsyringe is injected with pressure into the blood vessel of the humanbody by the chemical liquid injector.

Such a chemical liquid injector automatically injects the liquid at highpressure. For example, when the injection needle deviates from thevessel to leak under skin, an operator does not easily recognize itimmediately. To solve the problem, various leak detecting apparatuseshave been proposed for detecting leak of a liquid injected into a bloodvessel of a human body near the surface thereof through an injectionneedle (see, for example, patent documents 1 to 8 below).

Patent document 1: U.S. Pat. No. 6,408,204

Patent Document 2: U.S. Pat. No. 5,964,703

Patent Document 3: U.S. Pat. No. 5,947,910

Patent Document 4: U.S. Pat. No. 6,375,624

Patent Document 5: U.S. Pat. No. 5,954,668

Patent Document 6: U.S. Pat. No. 5,334,141

Patent Document 7: U.S. Pat. No. 4,647,281

Patent Document 8: U.S. Pat. No. 4,877,034

DISCLOSURE OF THE INVENTION Subject to be Solved by the Invention

The leak detecting apparatuses in above Patent Documents 1 to 3 detectleak of a liquid based on a change in impedance at a surface of a humanbody. The leak detecting apparatuses in Patent Documents 4 to 7 detectleak of a liquid based on a change in temperature of a tissue of a humanbody. The leak detecting apparatus in Patent Document 8 detects leak ofa liquid based on a change in optical characteristics of blood. However,human bodies have large individual variations, and the impedance, thetemperature, and the optical characteristics are changed with physicalcondition, so that the abovementioned leak detecting apparatuses cannoteasily detect leak of a liquid accurately and consistently.

The present invention has been made in view of the above-mentionedproblem, and it is an object thereof to provide a leak detectingapparatus which has a simple structure and has detection accuracy whichis reduced only slightly by disturbance.

Means to Solve the Subject

According to a first aspect to a fifth aspect, the present inventionprovides a leak detecting apparatus which includes a light ray emittingmeans, a light ray detecting means, a first measuring means, a secondmeasuring means, a ratio calculating means, a leak determining means,and a leak alarming means to detect leak of a liquid injected through aninjection needle to a blood vessel of a human body near the surfacethereof.

In the leak detecting apparatus according to the first aspect of thepresent invention, the light ray emitting means emits a light ray in apredetermined wavelength band containing a particular wavelength atwhich the reflectivity for the liquid is higher than the reflectivityfor internal tissues of the human body, to the human body at a positionthereof where the injection needle is inserted. The light ray detectingmeans detects the light ray in the wavelength band reflected inside thehuman body. The first measuring means measures the intensity of thedetected light ray at the particular wavelength, and the secondmeasuring means measures the average intensity of the detected light rayin the wavelength band. The ratio calculating means calculates the ratioof the intensity at the particular wavelength to the measured averageintensity. The leak determining means determines the occurrence of leakwhen the calculated ratio is higher than a predetermined referencevalue. The leak alarming means outputs and notifies a leak alarm whenthe occurrence of leak is determined. Thus, in the leak detectingapparatus, when the liquid injected into the blood vessel from theinjection needle is leaked, the leak alarm is output and notified byusing the increased intensity of the light ray at the particularwavelength reflected inside the human body as compared with the averageintensity in the wavelength band.

In the leak detecting apparatus according to the second aspect of thepresent invention, the light ray emitting means emits a light ray in apredetermined wavelength band containing a particular wavelength atwhich the reflectivity for the liquid is lower than the reflectivity forinternal tissues of the human body. When the calculated ratio is lowerthan a predetermined reference value, the occurrence of leak isdetermined. Thus, in the leak detecting apparatus, when the liquidinjected into the blood vessel from the injection needle is leaked, theleak alarm is output and notified by using the reduced intensity of thelight ray at the particular wavelength reflected inside the human bodyas compared with the average intensity in the wavelength band.

In the leak detecting apparatus according to the third aspect of thepresent invention, the light ray emitting means emits a light raycontaining a first particular wavelength at which the reflectivity forthe liquid is higher than the reflectivity for internal tissues of thehuman body and a second particular wavelength at which the reflectivityfor the liquid is approximately equal to the reflectivity for theinternal tissues of the human body. The second measuring means measuresthe intensity of the detected light ray at the second particularwavelength. The ratio calculating means calculates the ratio of theintensity at the first particular wavelength to the measured intensityat the second particular wavelength. The leak determining meansdetermines the occurrence of leak when the calculated ratio is higherthan a predetermined reference value. Thus, in the leak detectingapparatus, when the liquid injected into the blood vessel from theinjection needle is leaked, the leak alarm is output and notified byusing the increased intensity of the light ray at the first particularwavelength reflected inside the human body as compared with theintensity at the second particular wavelength.

In the leak detecting apparatus according to the fourth aspect of thepresent invention, the light ray emitting means emits a light raycontaining a first particular wavelength at which the reflectivity forthe liquid is lower than the reflectivity for internal tissues of thehuman body and a second particular wavelength at which the reflectivityfor the liquid is approximately equal to the reflectivity for theinternal tissues of the human body. The leak determining meansdetermines the occurrence of leak when the calculated ratio is lowerthan a predetermined reference value. Thus, in the leak detectingapparatus, when the liquid injected into the blood vessel from theinjection needle is leaked, the leak alarm is output and notified byusing the reduced intensity of the light ray at the first particularwavelength reflected inside the human body as compared with theintensity at the second particular wavelength.

In the leak detecting apparatus according to the fifth aspect of thepresent invention, the light ray emitting means emits a light raycontaining a first particular wavelength at which the reflectivity forthe liquid is higher than the reflectivity for internal tissues of thehuman body and a second particular wavelength at which the reflectivityfor the liquid is lower than the reflectivity for the internal tissuesof the human body. The leak determining means determines the occurrenceof leak when the calculated ratio is higher than a predeterminedreference value. Thus, in the leak detecting apparatus, when the liquidinjected into the blood vessel from the injection needle is leaked, theleak alarm is output and notified by using the increased intensity ofthe light ray at the first particular wavelength reflected inside thehuman body and the reduced intensity at the second particularwavelength.

Various means referred to in the present invention may be arranged toperform their functions, and may comprise dedicated hardware forperforming a predetermined function, a data processing apparatus whosepredetermined function is given by a computer program, a predeterminedfunction performed in a data processing apparatus according to acomputer program, or a combination thereof.

Various components referred to in the present invention do not need tobe a separate entity. A plurality of components may be constructed asone member, a single component may be constructed by a plurality ofmembers, a certain component may be part of another component, or acertain component may have a portion overlapping a portion of anothercomponent.

Effect of the Invention

In the leak detecting apparatus according to the first aspect of thepresent invention, when the liquid injected into the blood vessel fromthe injection needle is leaked, the leak alarm is output and notified byusing the increased intensity of the light ray at the particularwavelength reflected inside the human body as compared with the averageintensity in the wavelength band, so that the leak alarm can be outputand notified with high accuracy without being affected by variations inhuman body or physical condition.

In the leak detecting apparatus according to the second aspect of thepresent invention, when the liquid injected into the blood vessel fromthe injection needle is leaked, the leak alarm is output and notified byusing the reduced intensity of the light ray at the particularwavelength reflected inside the human body as compared with the averageintensity in the wavelength band, so that the leak alarm can be outputand notified with high accuracy without being affected by variations inhuman body or physical condition.

In the leak detecting apparatus according to the third aspect of thepresent invention, when the liquid injected into the blood vessel fromthe injection needle is leaked, the leak alarm is output and notified byusing the increased intensity of the light ray at the first particularwavelength reflected inside the human body as compared with theintensity at the second particular wavelength, so that the leak alarmcan be output and notified with high accuracy without being affected byvariations in human body or physical condition.

In the leak detecting apparatus according to the fourth aspect of thepresent invention, when the liquid injected into the blood vessel fromthe injection needle is leaked, the leak alarm is output and notified byusing the reduced intensity of the light ray at the first particularwavelength reflected inside the human body as compared with theintensity at the second particular wavelength, so that the leak alarmcan be output and notified with high accuracy without being affected byvariations in human body or physical condition.

In the leak detecting apparatus according to the fifth aspect of thepresent invention, when the liquid injected into the blood vessel fromthe injection needle is leaked, the leak alarm is output and notified byusing the increased intensity of the light ray at the first particularwavelength reflected inside the human body and the reduced intensity atthe second particular wavelength, so that the leak alarm can be outputand notified with high accuracy without being affected by variations inhuman body or physical condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the logical structure of achemical liquid injector integral with a leak detecting apparatusaccording to an embodiment of the present invention.

FIG. 2 is a block diagram showing the physical structure of a diagnosticimaging system.

FIG. 3 is a perspective view showing the outer appearance of thediagnostic imaging system.

FIG. 4 is a perspective view showing the outer appearance of thechemical liquid injector.

FIG. 5 are perspective views showing how the liquid syringe is mountedon an injection head.

FIG. 6 is a sectional view showing the internal structure of a leakdetecting unit.

FIG. 7 is a perspective view showing how the leak detecting unit ismounted on an arm portion of a human body.

FIG. 8 are graphs showing the detection results of infrared rays servingas light rays.

FIG. 9 is a flow chart showing the processing operation of the leakdetecting unit.

FIG. 10 is a flow chart showing the main routine in the processingoperation of an injection apparatus body.

FIG. 11 is a flow chart showing the sub routine of the injectionoperation.

FIG. 12 is a sectional view showing the internal structure of a leakdetecting unit formed in an experiment.

FIG. 13 are perspective views showing modifications of the leakdetecting unit.

DESCRIPTION OF REFERENCE NUMERALS

-   100 CHEMICAL LIQUID INJECTOR also serving as leak detecting    apparatus-   101 INJECTOR BODY doubling as detecting apparatus body-   103 LIQUID CRYSTAL DISPLAY serving as image display means-   131 WIRELESS RECEIVING UNIT serving as wireless receiving means-   141 LEAK ALARMING MEANS-   142 RECEPTION DETECTING MEANS-   143 STATE NOTIFYING MEANS-   144 RECEPTION ALARMING MEANS-   146 INJECTION STOPPING MEANS-   200 LIQUID SYRINGE-   211 CYLINDER MEMBER-   220 PISTON MEMBER-   421, 422, 600 LEAK DETECTING UNIT-   403 LIGHT-EMITTING DIODE corresponding to infrared ray emitting    means-   404, 630 PHOTOTRANSISTOR corresponding to infrared ray detecting    means-   409 WIRELESS TRANSMITTING UNIT serving as wireless transmitting    means-   411 FIRST MEASURING MEANS-   412 SECOND MEASURING MEANS-   413 RATIO CALCULATING MEANS-   414 LEAK DETERMINING MEANS-   500 ARM PORTION OF HUMAN BODY-   501 BLOOD VESSEL-   620 INFRARED RAY LED corresponding to infrared ray emitting means

BEST MODE FOR CARRYING THE INVENTION Configuration of Embodiment

An embodiment of the present invention will hereinafter be describedwith reference to the drawings. Although the directions of forward,rearward, leftward, rightward, upward, and downward are specified asshown in the embodiment, these directions are defined for convenience tofacilitate the description, and the definition does not limit anydirection in manufacture or actual use of the apparatus of the presentinvention.

As shown in FIGS. 1 to 3, chemical liquid injection system 1000 of theembodiment according to the present invention comprises chemical liquidinjector 100, liquid syringe 200, and CT scanner 300 which serves as adiagnostic imaging apparatus. The system is provided for takingdiagnostic images of a patient (not shown) injected with a liquid suchas a contrast medium, described later in detail.

As shown in FIGS. 2 and 3, CT scanner 300 includes diagnostic imagingunit 301 serving as a mechanism for performing imaging and imagingcontrol unit 302 such that diagnostic imaging unit 301 and imagingcontrol unit 302 are wire-connected through communication network 303.Diagnostic imaging unit 301 shoots a diagnostic image of a patient.Imaging control unit 302 controls the operation of diagnostic imagingunit 301.

As shown in FIG. 5, liquid syringe 200 comprises cylinder member 210 andpiston member 220 wherein piston member 220 is slidably inserted intocylinder member 210. Cylinder member 210 includes cylindrical hollowbody 211 which has conduit 212 formed at the closed leading end surface.

The trailing end of body 211 of cylinder member 210 is opened and pistonmember 220 is inserted from the opening into the interior of body 211.Cylinder member 210 has cylinder flange 213 formed in the outercircumference of the trailing end, and piston member 220 has pistonflange 221 formed in the outer circumference of the trailing end.

As shown in FIG. 4, chemical liquid injector 100 of the embodiment hasinjection control unit 101 and injection head 110 constructed asseparate components which are wire-connected through communication cable102. Injection head 110 is attached to the top end of caster stand 111by movable arm 112.

As shown in FIG. 5, head body 113 of injection head 110 has concaveportion 114 formed in its upper surface in a semi-cylindrical shapefitting cylinder member 210 of liquid syringe 200. Cylinder holdingmechanism 115 is formed in the forward section of concave portion 114for removably holding cylinder flange 211 of liquid syringe 200.

Piston driving mechanism 116 is placed in the rearward section ofconcave portion 114 of injection head 110 for holding and sliding pistonflange 221. Piston driving mechanism 116 removably holds and slidespiston member 220 of liquid syringe 200 in the forward and rearwarddirections.

In chemical liquid injector 100 of the embodiment, as shown in FIG. 7,liquid syringe 200 held by injection head 110 is connected to bloodvessel 501 of arm portion 500 of a human body through extension tube 211and injection needle 212, for example. Injection needle 212 is held byadhesive pad 213 formed of a transparent sheet through which infraredrays adequately pass.

As shown in FIG. 2, piston driving mechanism 116 has driving motor 117such as an ultrasonic motor as a driving source which is free fromgeneration of magnetic field even in operation, and slides piston member220 through a screw mechanism (not shown) or the like. Empty sensor 118is contained in piston driving mechanism 116 and detects the position ofslid piston flange 221 to sense the completion of liquid injection withliquid syringe 200.

Injection control unit 101 connected through communication cable 102 toinjection head 110 formed as described above contains a computer unit130 and is connected to imaging control unit 302 of CT scanner 300through communication network 304.

As shown in FIG. 4, injection control unit 101 has operation panel 103,liquid crystal display 104 serving as a data display means, speaker unit105 and the like, all of which are disposed on the front face of unithousing 106. Injection control unit 101 is wire-connected to controllerunit 107 as a separate component through connector 108.

Chemical liquid injector 100 of the embodiment is integral with a leakdetecting apparatus, and injection control unit 101 thereof also servesas the detecting apparatus body. Thus, leak detecting unit 401 is formedas a separate component from injection control unit 101 and wirelesslycommunicates with injection control unit 101.

For this reason, injection control unit 101 also contains wirelessreceiving unit 121 serving as a wireless receiving means whichwirelessly communicates with leak detecting unit 401. As shown in FIG.2, various devices such as wireless receiving unit 121 arewire-connected to computer unit 130.

Computer unit 130 is formed of a so-called one-chip microcomputerprovided with hardware such as CPU (Central Processing Unit) 131, ROM(Read Only Memory) 132, RAM (Random Access Memory) 133, I/F (Interface)134 and the like. Computer unit 130 has an appropriate computer programinstalled as firmware or the like in an information storage medium suchas ROM 132. CPU 131 executes various types of processing in accordancewith the computer program.

On the other hand, leak detecting unit 401 has unit housing 402 in a boxshape as shown in FIG. 6. Unit housing 402 contains light-emitting diode403 serving as a light emitting means and phototransistor 404 serving asa light detecting means such that they face downward.

Light-emitting diode 403 emits infrared rays as light rays in apredetermined wavelength band in a downward direction. Photodiode 404receives the infrared rays in the wavelength band from below. Morespecifically, the infrared rays emitted by light-emitting diode 403 areset in the wavelength band which is reflected uniformly by the internaltissues of arm portion 500, and the wavelength band includes aparticular wavelength at which infrared rays are absorbed at a high rateby a liquid such as a contrast medium and the reflectivity for a liquidsuch as a contrast medium is lower than the reflectivity for theinternal tissues of arm portion 500.

When the liquid is not leaked inside arm portion 500, the infrared raysin the wavelength band reflected inside arm portion 500 and thendetected have a substantially constant intensity as shown in FIG. 8( a).However, if the liquid is leaked inside arm portion 500, the infraredrays in the wavelength band reflected inside arm portion 500 and thendetected have an intensity which is extremely reduced only at theparticular wavelength as shown in FIG. 8( b).

Optical filter 406 is placed at a lower position opposite tolight-emitting diode 403 and phototransistor 404. Optical filter 406allows infrared rays only in the abovementioned wavelength band to passtherethrough. Circuit board 407 is placed in an upper portion withinleak detecting unit 401. As shown in FIG. 2, light-emitting diode 403,phototransistor 404, central processing unit 408, wireless transmittingunit 409 serving as a wireless transmitting means are mounted on circuitboard 407.

Central processing unit 408 is wire-connected to light-emitting diode403, phototransistor 404, and wireless transmitting unit 409, and causeslight-emitting diode 403 to continuously emit infrared rays andcontinuously takes the output from phototransistor 404. Centralprocessing unit 408 is formed as a logical circuit having apredetermined structure, and has various types of hardware functioningas first measuring means 411, second measuring means 412, ratiocalculating means 413, and leak determining means 414.

First measuring means 411 comprises, for example, an A/D(Analog/Digital) converter and an arithmetic processing circuit (notshown) and measures the intensity of light rays at the particularwavelength detected by phototransistor 404. Second measuring means 412also comprises an A/D converter, an arithmetic processing circuit andthe like, and measures the average intensity of the detected light raysin the wavelength band.

The intensity of light rays at the particular wavelength to be measuredas described above may be the intensity of light rays only at theparticular wavelength, or the average of light rays in a predeterminedrange of wavelengths centering on the particular wavelength, forexample. The average intensity of light rays in the wavelength band maybe the average of light rays in the entire wavelength band including theabovementioned particular wavelength, or the average of light rays otherthan a predetermined range centering on the particular wavelength in theabovementioned wavelength band, for example.

Ratio calculating means 413 and leak determining means 414 comprise apredetermined arithmetic processing circuit and the like. Ratiocalculating means 413 calculates the ratio of the intensity of themeasured light rays at the particular wavelength to the averageintensity in the wavelength band as described above. Leak determiningmeans 414 determines the occurrence of leak if the calculated ratio islower than a predetermined reference value.

Central processing circuit 408 causes wireless transmitting unit 409 tocontinuously transmit a predetermined standby signal through radio waveswhen leak determining means 414 does not determine the occurrence ofleak as described above. If the occurrence of leak is determined,central processing circuit 408 causes wireless transmitting unit 409 towirelessly transmit a predetermined alarm signal.

In chemical liquid injector 100 of the embodiment, microprocessor 130integrates and controls the respective components in accordance with thecomputer program as described above to have various means logically, asvarious functions, such as leak alarming means 141, reception detectingmeans 142, state notifying means 143, reception alarming means 144, andinjection stopping means 146, as shown in FIG. 1.

Leak alarming means 141 corresponds to the function of microprocessor130 which controls the operation of speaker unit 105 and liquid crystaldisplay 104 in accordance with the computer program. When the standbysignal wirelessly received by wireless receiving unit 121 is switched tothe alarm signal, leak alarming means 141 outputs and notifies the leakalarm with sound from speaker unit 105 and an image displayed on liquidcrystal display 104.

Reception detecting means 142 corresponds to the function ofmicroprocessor 130 which detects the data about the operation state ofwireless receiving unit 121, and detects the reception state of a radiosignal. State notifying means 143 corresponds to the function ofmicroprocessor 130 which controls the operation of liquid crystaldisplay 104, and outputs and notifies the reception state detected byreception detecting means 142 with an image displayed on liquid crystaldisplay 104 or the like.

Reception alarming means 144 corresponds to the function ofmicroprocessor 130 which controls the operation of speaker unit 105 andliquid crystal display 104, and outputs and notifies a reception alarmwith sound output from speaker unit 105 and an image displayed on liquidcrystal display 104 if the reception state detected by receptiondetecting means 142 is reduced below than a predetermined state.

Injection stopping means 146 corresponds to the function ofmicroprocessor 130 which controls the operation of driving motor 117 ofpiston driving mechanism 116, and stops driving motor 117 to stop theinjection of the liquid when at least one of the leak alarm and thereception alarm is output.

Although the abovementioned various means 141 to 146 of chemical liquidinjector 100 are accomplished by pieces of hardware such as speaker unit105 as required, they are mainly implemented by microprocessor 130functioning in accordance with the installed computer program.

Such a computer program is described to cause microprocessor 130 toperform processing operations including the output and notification ofthe leak alarm from speaker unit 105 and on liquid crystal display 104when wireless receiving unit 121 wirelessly receives the alarm signal,the stop of driving motor 117 in association with the output of the leakalarm, the detection of the reception state of wireless receiving unit121, the output and notification of the reception state on liquidcrystal display 104, the output and notification of the reception alarmfrom speaker unit 105 and on liquid crystal display 104 when thereception state is reduced than the predetermined state, and the stop ofdriving motor 117 in association with the output of the reception alarm.

For simplify the representation, control unit 302 and the whole chemicalliquid injector 100 are placed near diagnostic imaging unit 301 of CTscanner 300 in FIG. 3. However, for practical use in a medical facility,only injection head 110 is placed near diagnostic imaging unit 301, andcontrol unit 302 and injection control unit 101 are disposed in adifferent room.

Operation of the Embodiment

When chemical liquid injector 100 of the embodiment is used in theabovementioned arrangement, for example, an operator connects injectionneedle 212 through extension tube 211 to liquid syringe 200 filled witha liquid such as a contrast medium, and inserts injection needle 212into blood vessel 501 of arm portion 500 of a patient on diagnosticimaging unit 301 of CT scanner 300 and holds injection needle 212 withadhesive pad 213 as shown in FIG. 7.

Next, the operator places leak detecting unit 401 on the surface ofadhesive pad 213 with a restraint belt (not shown) or the like, andmounts liquid syringe 200 on injection head 110 of chemical liquidinjector 100. With this state, the operator turns on each power switch(not shown) of leak detecting unit 401 and injection control unit 101,and for example, sets an operation mode for using leak detecting unit401 on injection control unit 101 through a predetermined operation.

Then, as shown in FIG. 9, leak detecting unit 401 emits infrared rays inthe predetermined wavelength band from light-emitting diode 403 towardthe position where injection needle 212 is connected to blood vessel 501of arm portion 500 and detects the infrared rays with phototransistor404 (step S1). The intensity of the detected infrared rays at theparticular wavelength in the predetermined wavelength band is measured(step S2), and the average strength in the wavelength band is measured(step S3). The ratio of the intensity of the light rays at theparticular wavelength to the average intensity in the wavelength bandthus measured is calculated (step S4), and the calculated ratio iscompared with the predetermined reference value (step S5).

If the ratio is not lower than the reference value, the occurrence ofleak of the liquid is not determined, and leak detecting unit 401wirelessly transmits a standby signal representing “no leak” toinjection control unit 101 (step S6). On the other hand, if theabovementioned ratio is lower than the reference value, the occurrenceof leak of the liquid is determined (step S7), and leak detecting unit401 wirelessly transmits an alarm signal representing “occurrence ofleak” to injection control unit 101 (step S8).

Next, the method of detecting leak in chemical liquid injector 100 ofthe embodiment will hereinafter be described in brief. The infrared raysemitted by light-emitting diode 403 of leak detecting unit 401 are setin the wavelength band reflected uniformly by the internal tissues ofarm portion 500 as described above. The wavelength band includes theparticular wavelength at which the reflectivity for a predeterminedliquid such as a contrast medium is lower than the reflectivity for theinternal tissues of arm portion 500.

When the liquid is not leaked inside arm portion 500, the infrared raysin the wavelength band reflected inside arm portion 500 and thendetected have a substantially constant intensity as shown in FIG. 8( a).However, if the liquid is leaked inside arm portion 500, the infraredrays in the wavelength band reflected inside arm portion 500 and thendetected have an intensity which is extremely reduced only at theparticular wavelength as shown in FIG. 8( b).

The ratio of the intensity at the particular wavelength to the averageintensity in the wavelength band is approximately “1” when no liquid isleaked inside arm portion 500, but is extremely reduced below “1” whenthe liquid is leaked. Thus, in chemical liquid injector 100 of theembodiment, the abovementioned ratio is compared with the referencevalue such as “0.8” to determine whether or not the liquid is leakedwith high accuracy.

As shown in FIG. 10, injection control unit 101 continuously detects thereception state of radio waves in the operation state where leakdetecting unit 401 is used (step T1), and outputs by displaying thereception state in real time with a bar graph or the like on liquidcrystal display 104 (step T2).

With this operation, the operator can check the reception state of radiowaves from leak detecting unit 401 in real time while operatinginjection control unit 101, and performs the adjustment of injectioncontrol unit 101 or the position of leak detecting unit 401 if thereception state is not favorable.

When the detected reception state is reduced below the predeterminedstate as described above (step T3), injection control unit 101 outputs areception alarm such as “Radio wave reception impossible. Checkcommunication state” with display on liquid crystal display 104 andsound form speaker unit 105 (step T4).

Since injection control unit 101 does not accept any entry operation tostart injection before the reception state from leak detecting unit 401is changed to a favorable state (steps T3 to T5), it starts theinjection operation of the liquid only when the reception state isfavorable (step T6).

When injection control unit 101 receives entry operation to start theinjection of the liquid (steps T5 and T6), it continuously detects thereception state of radio waves, and outputs it by displaying on liquidcrystal display 104 in real time as shown in FIG. 11 (steps E1 and E2).

When the detected reception state is reduced below the predeterminedstate, it outputs and notifies the reception alarm on liquid crystaldisplay 104 and from speaker unit 105 (steps E3 and E4), and performsthe injection operation of the liquid only when the reception state isfavorable (steps E3 to E6).

Injection control unit 101 performs the injection operation in thefavorable reception state (step E6), and if the wirelessly receivedstandby signal is changed into the alarm signal (step E7), it outputs aleak alarm such as “Removal of injection needle detected. Checkinjection needle” with display on liquid crystal display 104 and soundfrom speaker unit 105 (step E8).

Since the injection operation of the liquid is stopped in this case(step E9), the liquid injection is not continued while injection needle212 comes off blood vessel 501. In addition, the abovementioned outputof the leak alarm is continued until predetermined reset operation isinput on injection control unit 101 (steps E10 and E11), the operatorrecognizes the leak alarm without fail.

In chemical liquid injector 100 of the embodiment, after the recognitionof the leak alarm, the operator appropriately inserts injection needle212 into blood vessel 501 and then makes entry operation to start theinjection of the liquid on operation panel 103. In response thereto, theliquid injection can be started again (steps T5 and 6).

When the operator makes entry operation to stop the injection (stepE12), injection control unit 101 stops the injection of the liquid (stepE9). When empty sensor 118 senses the completion of the injection of theliquid (step E13), injection control unit 101 ends the injection of theliquid (step E14).

Effect of the Embodiment

Chemical liquid injector 100 of the embodiment emits the infrared raysin the predetermined wavelength band including the particular wavelengthat which the reflectivity for the liquid is lower than the reflectivityfor the internal tissues within arm portion 500 as described above, anddetermines the occurrence of leak when the ratio of the intensity of theinfrared rays at the particular wavelength to the average intensity inthe wavelength band reflected inside arm portion 500 is reduced belowthe reference value.

For example, when the intensity of infrared rays reflected inside armportion 500 or the like is changed by variations in human body orphysical condition, that change affects the overall reflection intensityin the wavelength band but has substantially no effects on the ratio ofthe intensity at the particular wavelength to the average intensity inthe wavelength band. Thus, chemical liquid injector 100 of theembodiment can determine the leak of the liquid with high accuracy tooutput and notify the alarm without being affected by variations inhuman body or physical condition, and the operator can immediatelyrecognize removal of injection needle 212 from blood vessel 501 of thepatient and takes measures.

In chemical liquid injector 100 of the embodiment, if the removal ofinjection needle 212 is detected as described above, the injection ofthe liquid can be automatically stopped to automatically prevent theliquid injection from being continued while injection needle 212 comesoff blood vessel 501. In addition, light-emitting diode 403 emits theinfrared rays in the wavelength band reflected favorably inside armportion 500, and optical filter 406 allows only the infrared rays in thewavelength band to pass therethrough to phototransistor 404, therebymaking it possible to prevent the malfunction of detection of ambientlight noise by phototransistor 404.

In chemical liquid injector 100 of the embodiment, leak detecting unit401 including light-emitting diode 403, phototransistor 404, wirelesstransmitting unit 409 and the like is formed separately from injectioncontrol unit 101 including wireless receiving unit 121, liquid crystaldisplay 104, speaker unit 105 and the like.

When leak detecting unit 401 detects the leak of the liquid, injectioncontrol unit 101 outputs and notifies the leak alarm through wirelesscommunication. This allows leak detecting unit 401 directly mounted onthe human body to be reduced in size and weight to facilitate handling,and the leak alarm can be recognized without fail by the operator who islocated away from leak detecting unit 401 and manually operatesinjection control unit 101.

Injection control unit 101 continuously detects the reception state ofthe radio signal from leak detecting unit 401 and outputs the receptionstate in real time. Thus, the operator can always know the communicationstate between leak detecting unit 401 and injection control unit 101,and if the communication state is not favorable, the operator can dealwith that before the injection operation is performed.

Since injection control unit 101 outputs and notifies the receptionalarm when the detected reception state is reduced below thepredetermined state, it is possible to prevent the situation in whichthe alarm signal cannot be wirelessly received due to poor communicationand thus the leak alarm is not output. In addition, the liquid injectionis stopped when at least one of the leak alarm and the reception alarmis output, so that it is possible not only to automatically prevent thecontinuous liquid injection while injection needle 212 is removed fromblood vessel 501, but also to prevent the continuous liquid injectionwhile the alarm signal cannot be wirelessly received.

The inventors have experimentally checked whether or not a contrastmedium leaked in a human body can be detected with infrared rays. In theexperiment, first, a light source capable of emitting light rays atwavelengths of approximately 450 nm to 1350 nm was prepared, and thelight source was placed at one end of a light-shield container and aspectrometer was disposed at the other end. Then, the intensity of lightrays was measured by the spectrometer for each wavelength in the statewhere the container was filled with air as a reference, the state wherethe container was filled with water substituting for a human body, andthe state where the container was filled with a typical contrast mediumfor CT. It was revealed that the contrast medium adequately absorbed thelight rays at a wavelength near 950 nm as compared with the air andwater.

Since a human body adequately transmits infrared rays at wavelengths ofapproximately 800 to 1000 nm, the inventors performed a secondexperiment by using an infrared LED (Light-Emitting Diode) with a peakwavelength of 950 nm as a light source. In the second experiment, afirst chicken piece was placed at the bottom of a light-shield containerand the container was sealed by a first acrylic plate. A second acrylicplate was disposed in parallel with the first acrylic plate such thatthey are spaced from each other, and a second chicken piece was placedon the surface of the second acrylic plate. A model of a human body wasformed in this manner (not shown).

An infrared LED with a peak wavelength of 950 nm and a spectrometer wereplaced in parallel to form a trial detecting unit (not shown) similar toleak detecting unit 401 of the embodiment. The trial detecting unit wasplaced in intimate contact with the surface of the second chicken pieceof the human body model. Then, the intensity of the infrared rays wasmeasured by the spectrometer for each wavelength in the state where thehuman body model was filled with air, the state where the model wasfilled with water, and the state where the model was filled a contrastmedium. It was revealed that the detected intensity of the contrastmedium was extremely reduced near at a wavelength of 950 nm as comparedwith the air and water.

In other words, in leak detecting unit 401 of the embodiment, theinfrared LED with a peak wavelength of 950 nm was used as light-emittingdiode 401 and phototransistor 404 detects the intensity of infrared raysat the wavelength of 950 nm, for example, thereby allowing favorabledetermination of leak of the contrast medium. Since the infrared LEDwith a peak wavelength of 950 nm as described above is commerciallyavailable as a product, such a product can be used to implement leakdetecting unit 401 of the embodiment with favorable productivity.

After seeing the foregoing results, the inventors manufactured leakdetecting unit 600 by way of trial as shown in FIG. 12 to perform athird experiment. Leak detecting unit 600 has unit housing 610 in a boxshape. Unit housing 610 contains infrared LED 620 with a peak outputwavelength of 950 nm and phototransistor 630 with a peak detectionwavelength of 880 nm such that they face downward.

Unit housing 610 has circular opening holes 611 and 612 at positionsopposite to infrared LED 620 and phototransistor 630 at the bottomplate, respectively. Transparent sheet 613 made of resin such as PET(Polyethylene Terephthalate) and PS(Poly-Styrene) is placed over theentire bottom surface.

Enlarging and reducing opening hole 612 opposite to phototransistor 630increases and reduces the amount of received light, but the effects ofnoise due to the surface state or the like of the human body are alsoincreased and reduced, so that an extremely large or small size ofopening hole 612 does not provide excellent detection sensitivity. Theinventors performed an experiment to see the detection sensitivity withdiameters of opening hole 612 of 1.0 mm, 1.5 mm, and 3.0 mm. Theresulting S/N ratios (Signal-to-Noise ratio) were 1.8, 5.0, and 3.0,with the maximum level at the diameter of 1.5 mm.

In the environment where leak detecting unit 600 as described above isused, a fluorescent lamp is typically used as illumination. Theinventors investigated spectral characteristics of a typical whitefluorescent lamp and found that the typical white fluorescent lamphardly output light rays at wavelengths of 800 nm or longer. In otherwords, it was shown that leak detecting unit 600 for detecting liquidleak at a wavelength of 950 nm as described above can favorably functionwithout being affected by outside light in a typical environment wherethe white fluorescent lamp is used as illumination.

Modifications of the Embodiment

The present invention is not in any way limited to the above-mentionedembodiment, but various changes and modifications may be made thereinwithout departing from the scope of the invention. For example, in theabove embodiment, the leak detecting apparatus is formed integrally withchemical liquid injector 100. The leak detecting apparatus may be formedseparately from chemical liquid injector 100.

Since the injection of the liquid must be stopped immediately after theleak of the liquid is detected as described above, the leak detectingapparatus formed integrally with chemical liquid injector 100 iseffective. Thus, if the leak detecting apparatus is formed separatelyfrom chemical liquid injector 100, chemical liquid injector preferablystops the injection operation in association with output of an alarmfrom the leak detecting apparatus.

In the above embodiment, chemical liquid injector 100 outputs andnotifies the leak alarm and the reception alarm. For example, the alarmmay be transmitted as data to control unit 302 of CT scanner 300 andoutput and notified on liquid crystal display 304. Since control unit302 is placed in a different room from diagnostic imaging unit 301 asdescribed above, notifying diagnostic imaging unit 301 of the alarm iseffective.

In the above embodiment, only chemical liquid injector 100 stops theinjection operation in response to the leak alarm. For example, CTscanner 300 may also stop the imaging operation in association with thestop of the operation of chemical liquid injector 100 described above.In this case, chemical liquid injector 100 may directly transmit thealarm signal of leak detecting unit 401 as data to CT scanner 300, ormay indirectly transfer it as data via injection control unit 101.

The above embodiment assumes that chemical liquid injector 100 is usednear CT scanner 300, but it may be used near a CT scanner, a PETapparatus, an angiography apparatus, an MRA apparatus, an ultrasonicdiagnostic apparatus, or the like. In the above embodiment, leakdetecting unit 401 and injection control unit 101 wirelessly communicatewith each other through radio signals. The communication method may berealized with wireless communication of ultrasonic signals, wirelesscommunication of optical signals, wire communication of electricsignals, wire communication of optical signals, or the like.

In the above embodiment, one light-emitting diode 403 and onephototransistor 404 are mounted on leak detecting unit 401.Alternatively, it is possible to leak detecting unit 421 which includesa plurality of light-emitting diodes 403 and a plurality ofphototransistors 404 arranged therein as shown in FIG. 13( a), or leakdetecting unit 422 which includes a plurality of phototransistors 404around one light-emitting diode 403 arranged therein as shown in FIG.13( b). Since such a leak detecting apparatus can detect leak of aliquid at a plurality of positions, the leak of the liquid can bedetected more satisfactorily.

In the above embodiment, chemical liquid injector 100 causes leakalarming means 141 to output and notify only the leak alarm with animage displayed on liquid crystal display 104 or the like. For example,a graph displaying means (not shown) may be used to output and display agraph of distribution of intensity as shown in FIGS. 8( a) and 8(b) onliquid crystal display 104.

In the above embodiment, the only one particular wavelength is containedin the predetermined wavelength band of the infrared rays, but aplurality of particular wavelengths may be used. In this case, since theintensity can be measured for each of the plurality of particularwavelengths and the ratio can be calculated for each of the plurality ofintensities, the occurrence of leak may be determined when all of theplurality of ratios are higher than a reference value, for example. Theoccurrence of leak is determined with the plurality of particularwavelengths in this case, so that the occurrence of false detection canbe reduced to improve the accuracy of detection.

A failure to detect liquid leak may be prevented by determining theoccurrence of leak if one of the plurality of ratios is higher than thereference value. In addition, both of the false detection and thefailure to detect liquid leak may be prevented favorably by determiningthe occurrence of leak if a predetermined number of the plurality ofratios are higher than the reference value or if the majority of theplurality of ratios are higher than the reference value. When thepredetermined wavelength band of the infrared rays contains theplurality of particular wavelengths as described above, the plurality ofcalculated ratios may be individually compared with specific referencevalues to improve the accuracy of determination of occurrence of leak.

In the above embodiment, light-emitting diode 403 emits the infraredrays in the predetermined wavelength band containing the particularwavelength at which the reflectivity for the liquid is lower than thereflectivity for the internal tissues of arm portion 500, and theoccurrence of leak is determined if the intensity of the infrared raysat the particular wavelength reflected inside arm portion 500 is lowerthan the average intensity in the wavelength band.

Alternatively, light-emitting diode 403 emits infrared rays in awavelength band containing a particular wavelength at which thereflectivity for the liquid is higher than the reflectivity for theinternal tissues of arm portion 500, and the occurrence of leak isdetermined if the ratio of the intensity of the infrared rays at theparticular wavelength to the average intensity in the wavelength bandreflected inside arm portion 500 is higher than a reference value.

It is also possible that light-emitting diode 403 emits infrared rayscontaining a first particular wavelength at which the reflectivity forthe liquid is higher than the reflectivity for the internal tissues ofarm portion 500 and a second particular wavelength at which thereflectivity for the liquid is approximately equal to the reflectivityfor the internal tissues, and the occurrence of leak is determined ifthe reflected intensity at the first particular wavelength to thereflected intensity at the second particular wavelength is higher than areference vale.

It is also possible that light-emitting diode 403 emits infrared rayscontaining a first particular wavelength at which the reflectivity forthe liquid is lower than the reflectivity for the internal tissues ofarm portion 500 and a second particular wavelength at which thereflectivity for the liquid is approximately equal to the reflectivityfor the internal tissues, and the occurrence of leak is determined ifthe reflected intensity at the first particular wavelength to thereflected intensity at the second particular wavelength is lower than areference vale.

It is also possible that light-emitting diode 403 emits infrared rayscontaining a first particular wavelength at which the reflectivity forthe liquid is higher than the reflectivity for the internal tissues ofarm portion 500 and a second particular wavelength at which thereflectivity for the liquid is lower than the reflectivity for theinternal tissues, and the occurrence of leak is determined if thereflected intensity at the first particular wavelength to the reflectedintensity at the second particular wavelength is higher than a referencevale.

In the structure in which the wavelength band contains the first andsecond particular wavelengths as described above, it is possible thatonly the first particular wavelength is realized by a plurality ofwavelengths, and the ratios of the reflected intensities at theplurality of first particular wavelengths to the reflected intensity atthe second particular wavelength are individually compared with aplurality of reference values. It is also possible that only the secondparticular wavelength is realized by a plurality of wavelengths, and theratios of the reflected intensity at the first particular wavelength tothe reflected intensities at the plurality of second particularwavelengths are individually compared with a plurality of referencevalues. Alternatively, each of the first and second particularwavelengths may be realized by a plurality of wavelengths, and theratios of the reflected intensities at the plurality of firstwavelengths to the reflected intensities at the plurality of secondparticular wavelengths may be individually compared with a plurality ofreference values.

In the above embodiment, when the leak of the liquid is detected,chemical liquid injector 100 stops piston driving mechanism 116 todiscontinue the liquid injection. For example, the leak detectingapparatus may include a standalone tube blocking means (not shown) forblocking extension tube 211 when leak of the liquid is detected.

Such a tube blocking means is formed as a standalone unit structurewhich is mounted on extension tube 211, and performs wireless and wirecommunication with leak detecting unit 401 and the detecting apparatusbody, for example. The tube blocking means also includes a mechanism foropening or closing extension tube 211 with a driving source such as asolenoid, and blocks extension tube 211 when the leak of the liquid isdetected. In such a leak detecting apparatus, extension tube 211 isblocked independently when the liquid leak is detected, so that theliquid injection can be stopped automatically even when chemical liquidinjector 100 does not operate in association with the leak detectingapparatus, for example.

In the above embodiment, microprocessor 130 functions in accordance withthe installed computer program to logically realize various means 141 to146 of injection control unit 101. For example, at leas some of variousmeans 141 to 144 may be formed by hardware such as a dedicated logicalcircuit.

In contrast, in the above embodiment, various means 411 to 414 of leakdetecting unit 401 are formed by the predetermined hardware, but variousmeans 411 to 414 may be logically realized by a microprocessor whichfunctions in accordance with an installed computer program, for example.

In the above embodiment, one liquid syringe 200 is mounted in oneconcave portion 114 of chemical liquid injector 100, but a plurality ofliquid syringes 200 may be mounted in a plurality of concave portions ofthe injection head (not shown). In the above embodiment, liquid syringe200 is directly mounted on chemical liquid injector 100. Since liquidsyringes 200 of various sizes are commercially available, it is possiblethat only liquid syringe 200 of the maximum size is directly mounted onchemical liquid injector 100 and liquid syringes 200 of the varioussizes other than the maximum size are mounted on chemical liquidinjector 100 via dedicated cylinder adapters (not shown).

1. A leak detecting apparatus which detects leak of a liquid injectedthrough an injection needle into a blood vessel of a human body near asurface thereof, comprising: at least one light ray emitting means foremitting a light ray in a predetermined wavelength band containing atleast one particular wavelength at which the reflectivity for the liquidis higher than the reflectivity for internal tissues of the human body,to the human body at a position thereof where the injection needle isinserted; at least one light ray detecting means for detecting the lightray in the wavelength band reflected inside the human body; firstmeasuring means for measuring the intensity of the detected light ray atthe particular wavelength; second measuring means for measuring theaverage intensity of the detected light ray in the wavelength band;ratio calculating means for calculating the ratio of the intensity atthe particular wavelength to the measured average intensity; leakdetermining means for determining occurrence of leak when the calculatedratio is higher than a predetermined reference value; and leak alarmingmeans for outputting and notifying a leak alarm when the occurrence ofleak is determined.
 2. The leak detecting apparatus according to claim1, wherein the light ray emitting means emits the light ray at aplurality of the particular wavelengths, the first measuring meansmeasures the intensity for each of the plurality of particularwavelengths, and the ratio calculating means calculates the ratio foreach of the plurality of intensities.
 3. The leak detecting apparatusaccording to claim 2, wherein the leak determining means determinesoccurrence of leak when at least one of the plurality of ratios ishigher than the predetermined reference value.
 4. The leak detectingapparatus according to claim 3, wherein the leak determining meansindividually compares the plurality of ratios with the predeterminedreference values specific to the ratios.
 5. The leak detecting apparatusaccording to claim 1, further comprising a leak detecting unit whichcomprises at least the light ray emitting means and the light raydetecting means; and a detecting apparatus body formed separately fromthe leak detecting unit and comprising at least the leak alarming means,wherein the leak detecting unit comprises wireless transmitting meansfor transmitting a wireless signal, and the detecting apparatus bodycomprises wireless receiving means for receiving the wireless signal. 6.The leak detecting apparatus according to claim 5, wherein the detectingapparatus body comprises: reception detecting means for detecting thereception state of the wireless signal; and state notifying means foroutputting and notifying the detected reception state.
 7. The leakdetecting apparatus according to claim 6, wherein the detectingapparatus body further comprises reception alarming means for outputtingand notifying a reception alarm when the detected reception state islower than a predetermined state.
 8. The leak detecting apparatusaccording to claim 1, wherein the leak detecting apparatus comprises aplurality of the light ray emitting means and/or a plurality of thelight ray detecting means.
 9. The leak detecting apparatus according toclaim 1, further comprising an extension tube connected to the injectionneedle for flowing the liquid; and tube blocking means for blocking theextension tube when the difference exceeds the allowable range.
 10. Achemical liquid injector for inserting a piston member with pressureinto a cylinder member filled with a liquid in a liquid syringeconnected to a human body through an injection needle and an extensiontube, comprising: the leak detecting apparatus according to claim 1; andinjection stopping means for stopping injection of the liquid when theleak detecting apparatus outputs and notifies the leak alarm.
 11. Achemical liquid injector for inserting a piston member with pressureinto a cylinder member filled with a liquid in a liquid syringeconnected to a human body through an injection needle and an extensiontube, comprising: the leak detecting apparatus according to claim 7; andinjection stopping means for stopping injection of the liquid when theleak detecting apparatus outputs and notifies at least one of the leakalarm and the reception alarm.
 12. A method for detecting a leak of aliquid injected through an injection needle into a blood vessel of ahuman body near a surface thereof, comprising: emitting a light ray in apredetermined wavelength band containing at least one particularwavelength at which the reflectivity for the liquid is higher than thereflectivity for internal tissues of the human body, to the human bodyat a position thereof where the injection needle is inserted; detectingthe light ray in the wavelength band reflected inside the human body;measuring the intensity of the detected light ray at the particularwavelength; measuring the average intensity of the detected light ray inthe wavelength band; calculating the ratio of the intensity at theparticular wavelength to the measured average intensity; determiningoccurrence of leak when the calculated ratio is higher than apredetermined reference value; and outputting and notifying a leak alarmwhen the occurrence of leak is determined.
 13. The method according toclaim 12, wherein the light ray is emitted at a plurality of theparticular wavelengths, the intensity for each of the plurality ofparticular wavelengths is measured, and the ratio for each of theplurality of intensities is calculated.
 14. The method according toclaim 13, wherein the occurrence of the leak is determined when at leastone of the plurality of ratios is higher than the predeterminedreference value.
 15. The method according to claim 14, wherein theplurality of ratios are individually compared with the predeterminedreference values specific to the ratios.
 16. The method according toclaim 12, wherein a wireless signal is transmitted to output and notifythe leak.
 17. The method according to claim 12, wherein an extensiontube is connected to the injection needle for flowing the liquid, saidmethod further comprising blocking the extension tube when theoccurrence of a leak is determined.